Procedures for assessment of cumulative impacts of coal mining on the hydrologic balance

Techniques were developed to assess the probable cumulative impacts of anticipated surface mining upon the hydrology of and area. An activity profile of cumulative drainage area versus river miles downstream from the surface mining site is constructed that shows major water uses, flood prone areas, and stream classifications. From the summary shown by the activity profile, an impact matrix is used as a checklist for the importance of the impacts under categories such as water supply, flood prone areas, water contact recreation, etc. Based on the categories checked on the impact matrix, a simple, less accurate model or a more comprehensive and accurate one can be used to quantify the impacts. Quantified impacts are then displayed on an impact profile showing the percentage change in a hydrologic characteristic versus distance downstream of the surface mining site. The simple model for quantification considers only dilution from tributary areas during critical periods whereas the comprehensive model routes flows and quality of water continuously through the year and considers, in addition to dilution, instream processes such as settling, biological uptake , and chemical reactions. (USGS)